Development of the control system for electron cyclotron resonance heating on J-TEXT tokamak.

A 105 GHz/500 kW/1 s electron cyclotron resonance heating (ECRH) system has been developed on J-TEXT tokamak since 2017. The core component of the ECRH system is a gyrotron manufactured by Gyrotron Complexes Ltd. (GYCOM Ltd.), which generates microwaves of a certain frequency and power. To guarantee safe and stable operation, it is necessary to design a specialized control system. The control system is expected to perform time sequence trigger, protection, signal monitoring, communication, and data acquisition. The hardware is built with real-time processors and data acquisition modules from National Instruments. The control program is realized by LabVIEW. Test results indicate that the control system can commit stable and safe operation of the gyrotron, which guarantees the integrated commissioning tests of the whole ECRH system and ECRH related physics experiments. Under the operation of this control system, the gyrotron can generate microwaves as expected, and the ECRH system is well protected when a fault takes place.

Synthesis of two quasi-optical polarizers for the multi-frequency high-power millimeter wave system.

Millimeter wave systems based on powerful gyrotron can deliver megawatt microwave power, which is an important auxiliary heating method for magnetic confinement fusion devices. Reflective gratings are normally used as quasi-optical polarizers for polarization control of the wave in such systems. Based on the coordinate transformation method, we developed a numerical code to study the broadband polarization strategy. By considering the synthesis of two polarizers, we designed a pair of polarizers in the W band. Calculation results indicated that almost arbitrary polarization can be achieved in a wide frequency range. To verify the design, we set up a low-power test platform and experiments were carried out. The performance of the polarizers was tested from 80 to 105 GHz with a step of 5 GHz. The test results agreed well with the numerical results, indicating that the design is reasonable. With the development of multi-frequency gyrotrons, the study in this paper can be used as a reference for the design of broadband polarizers of multi-frequency millimeter wave systems.

The coordinate transformation method for design of polarizers on HL-2A electron cyclotron resonance heating and current drive systems.

Polarizers are widely used to change the polarization of millimeter waves on the electron cyclotron resonance heating and current drive (ECRH and CD) systems. A new method based on the coordinate transformation and the Fourier expansion (the so-called C-method) has been developed for design of polarizers on the HL-2A ECRH and CD systems. This method transforms the grating problem to an eigenvalue problem, making it easy and clear to understand and solve. The comparison between the C-method, the integral method, and the low power test results is presented. It indicates that the C-method can be considered as a rigorous numerical method for the design of polarizers. Finally, two polarizers were designed based on the C-method which can be used together to achieve almost arbitrary polarization.

New printed circuit boards magnetic coils in the vacuum vessel of J-TEXT tokamak for position measurement.

Four sets of magnetic diagnostic coils, which are printed on machinable ceramic printed circuit boards (PCB), are designed, fabricated, installed, and tested in the Joint Texas Experimental Tokamak (J-TEXT) vacuum vessel for detecting the plasma radial and vertical displacements relative to the geometric center of the vacuum vessel in Ohmic discharges. Each coordinate is determined by a pair of variable cross-section Rogowski and saddle coils, which measure the tangential and normal magnetic fields (relative to the coil surface). These coils are suitable for mass production and offer advantages in vacuum compatibility and temperature tolerance that are important for J-TEXT. Position measurements using PCB coils are compared with those from soft x-ray image system and match the position well.

High cure rate of Helicobacter pylori infection using tripotassium dicitrato bismuthate, furazolidone and clarithromycin triple therapy for 1 week.

BACKGROUND: When metronidazole is used in bismuth-based or proton pump inhibitor-based triple therapy, the cure rate of Helicobacter pylori is usually high. However, metronidazole-resistant H. pylori strains, which are increasing in frequency, are a major cause of failed H. pylori eradication. AIM: To evaluate the efficacy of non-metronidazole containing bismuth-based triple therapy for H. pylori infection. METHODS: One-hundred and eighty H. pylori-positive patients with endoscopically documented peptic ulcer disease or functional dyspepsia were randomly assigned to one of three 1-week regimens containing tripotassium dicitrato bismuthate (also called colloidal bismuth subcitrate) 240 mg b.d. and two antibiotics: furazolidone 100 mg b.d. plus clarithromycin 250 mg b.d. (Group A); or clarithromycin 250 mg b.d. plus amoxycillin 1000 mg b.d. (Group B); or furazolidone 100 mg b.d. plus josamycin 1000 mg b.d. (Group C). H. pylori status was assessed by rapid urease test, histology and culture of gastric biopsy specimens taken from both the antrum and corpus, both before and at least 4 weeks after completion of therapy. RESULTS: Thirteen patients dropped out (3 in group A, 5 in group B and 5 in group C). Based on an intention-to-treat analysis, the eradication rates achieved in groups A, B and C were 88% (53/60), 58% (35/60) and 77% (46/60), respectively. These differences were significant between groups A and B (P < 0.001), as well as between groups B and C (P < 0.05). Side-effects occurred in 7 (12%) patients in group A, 3 (5%) in group B and 8 (13%) in group C, and were mild, with the exception of vomiting in one patient (group C) that resulted in withdrawal from the study. CONCLUSION: One-week triple therapy, consisting of tripotassium dicitrato bismuthate, low-dose furazolidone and low-dose clarithromycin, achieves a high cure rate of H. pylori.

The efficacy of furazolidone and metronidazole in the treatment of chronic gastritis associated with Helicobacter (Campylobacter) pylori--a randomized double-blind placebo-controlled clinical trial.

Seventy-two patients with Helicobacter pylori-associated chronic gastritis were randomized to a 3-week oral treatment with furazolidone 0.1g t.i.d. or metronidazole 0.2g t.i.d. or placebo. Endoscopy was performed before and after treatment, and biopsy specimens were taken from the antrum of the stomach for histological examination and culture of Helicobacter pylori. Disappearance rates of Helicobacter pylori in furazolidone, metronidazole and the control groups were 74% (20/27) if considering completion of therapy, the 20/25 or 80%, 33.3% (8/24) and 14.3% (3/21) respectively. There was a significant difference in the disappearance rate of Helicobacter pylori between furazolidone and metronidazole, and between furazolidone and the placebo group (p less than 0.01), but there was no such difference between metronidazole and the placebo group (p greater than 0.05). In the patients receiving furazolidone, the eradication of Helicobacter pylori was accompanied by marked improvement in both inflammatory infiltration in the gastric mucosa and symptoms. These results reasonably suggest that Helicobacter pylori may play an etiological role in the pathogenesis of chronic gastritis, and that furazolidone is effective in the treatment of Helicobacter pylori-associated chronic gastritis.